Dual-loop torque sensing system and method thereof

Abstract

A dual-loop torque sensing system includes four position sensors disposed in the motor and the reduction drive to form a dual-loop for detection to calculate the output torques. The detection of the position sensors is for confirming abnormality of the dual-loop or the position sensors. A failure alarm is issued to enhance the safety of the working environment.

What is claimed is: 
     
       1. A dual-loop torque sensing system, comprising:
 a reduction drive coupled to a first position sensor and a second position sensor, and configured to reduce an output torque, wherein the first position sensor and the second position sensor are configured to detect a rotation state of the reduction drive; 
 a motor coupled to the reduction drive, a third position sensor and a fourth position sensor, wherein the third position sensor and the fourth position sensor are configured to detect a motor rotating state; 
 a first sensing loop having the first position sensor and the third position sensor disposed thereon; 
 a second sensing loop having the second position sensor and the fourth position sensor disposed thereon; and 
 a control device coupled to the first sensing loop and the second sensing loop, comprising:
 a reading circuit coupled to the first position sensor, the second position sensor, the third position sensor and the fourth position sensor, and configured to read detection values; 
 a calculation circuit coupled to the reading circuit, and configured to receive the detection values for torque calculation to generate a calculation result; 
 a comparison circuit coupled to the calculation circuit, and configured to receive the calculation result of the calculation circuit and to output an identification signal or a normal signal according to the calculation result; 
 a search circuit coupled the comparison circuit, and configured to receive the identification signal, search for abnormal position sensors according to the identification signal, and output a search signal; and 
 a torque output circuit coupled to the search circuit and the comparison circuit, and configured to receive the search signal or the normal signal, and output a first torque value according to detection values of the first sensing loop and/or output a second torque value according to detection values of the second sensing loop. 
 
 
     
     
       2. The dual-loop torque sensing system of  claim 1 , wherein the calculation circuit receives a first detection value P 1  generated by the first position sensor detecting the reduction drive, and a third detection value P 3  generated by the third position sensor detecting the motor, and calculates the first torque value F 1 =K×(P 1 −P 3 ×N/360) according to a reducer parameter K and a reduction ratio N of the reduction drive. 
     
     
       3. The dual-loop torque sensing system of  claim 1 , wherein the calculation circuit receives a second detection value P 2  generated by the second position sensor detecting the reduction drive and a fourth detection value P 4  generated by the fourth position sensor detecting the motor, and calculates the second torque value F 2 =K×(P 2 −P 4 ×N/360) according to a reducer parameter K and a reduction ratio N of the reduction drive. 
     
     
       4. The dual-loop torque sensing system of  claim 1 , wherein the reading circuit reads detection values of the first position sensor and the second position sensor coupled to the reduction drive, and the third position sensor and the fourth position sensor coupled to the motor at a beginning and an end of a preset time period, and the calculation circuit calculates a first absolute speed value, a second absolute speed value, a third absolute speed value, and a fourth absolute speed value corresponding to each corresponding position sensor according to a length of the preset time period, the detection values, and a reduction ratio, and determines abnormality of each position sensor according the first absolute speed value, the second absolute speed value, the third absolute speed value, and the fourth absolute speed value. 
     
     
       5. The dual-loop torque sensing system of  claim 4 , wherein:
 the comparison circuit receives the first absolute speed value and the second absolute speed value, calculates an absolute difference between the first absolute speed value and the second absolute speed value, and determines whether the absolute difference between the first absolute speed value and the second absolute speed value is less than a threshold value to determine whether the first position sensor and/or the second position sensor is abnormal; and 
 the comparison circuit receives the third absolute speed value and the fourth absolute speed value, calculates an absolute difference between the third absolute speed value and the fourth absolute speed, and determines whether the absolute difference between the third absolute speed value and the fourth absolute speed is less than the threshold value to determine whether the third position sensor and/or the fourth position sensor is abnormal. 
 
     
     
       6. The dual-loop torque sensing system of  claim 5 , wherein when the comparison circuit determines the first position sensor, the second position sensor, the third position sensor and the fourth position sensor are normal, the normal signal is issued to the torque output circuit. 
     
     
       7. The dual-loop torque sensing system of  claim 5 , wherein when the comparison circuit determines the first position sensor, the second position sensor, the third position sensor and/or the fourth position sensor is abnormal, an identification signal is issued to the search circuit to search for an abnormal position sensor. 
     
     
       8. A method for the dual-loop torque sensing system, the system comprising a reduction drive coupled to a first position sensor and a second position sensor, a motor coupled to the reduction drive, a third position sensor and a fourth position sensor, a first sensing loop having the first position sensor and the third position sensor, a second sensing loop having the second position sensor and the fourth position sensor, and a control device coupled to the first sensing loop and the second sensing loop, the control device comprising a reading circuit coupled to the first position sensor, the second position sensor, the third position sensor and the fourth position sensor, a calculation circuit coupled to the reading circuit, a comparison circuit coupled to the calculation circuit, a search circuit coupled the comparison circuit, and a torque output circuit coupled to the search circuit and the comparison circuit, the method comprising:
 reading detection values of the first, second, third and fourth position sensors at a beginning of a preset time period; 
 reading detection values of the first, second, third and fourth position sensors at an end of the preset time period; and 
 calculating a first absolute speed value, a second absolute speed value, a third absolute speed value and a fourth absolute speed value corresponding to the four position sensors according to detection values read at the beginning and the end of the preset time period, a reduction ratio and a length of the preset time period; 
 determining the position sensors coupled to the motor and the position sensors coupled to the reduction drive are normal if an absolute difference between the first absolute speed value and the second absolute speed value is less than a threshold value, and an absolute difference between the third absolute speed value and the fourth absolute speed value is less than the threshold value; and 
 outputting a first torque value and a second torque value. 
 
     
     
       9. The method of  claim 8 , further comprising if the absolute difference between the first absolute speed value and the second absolute speed value and the absolute difference between the third absolute speed value and the fourth absolute speed value is greater than the threshold value, determining at least two of the first position sensor, the second position sensor, the third position sensor, and the fourth position sensor are abnormal, and issuing a notification signal to stop a robotic arm. 
     
     
       10. The method of  claim 8 , further comprising if the absolute difference between the first absolute speed value and the second absolute speed value or the absolute difference between the third absolute speed value and the fourth absolute speed value is greater than the threshold value, determining at least one of the first position sensor, the second position sensor, the third position sensor, and the fourth position sensor is abnormal. 
     
     
       11. The method of  claim 10 , further comprising when the absolute difference between the first absolute speed value and the second absolute speed value is greater than the threshold value, setting the third absolute speed value or the fourth absolute speed value as a search threshold value to determine which of the first position sensor and the second position sensor is abnormal accordingly. 
     
     
       12. The method of  claim 11  further comprising when the search threshold value is between the first absolute speed value and the second absolute speed value, determining whether an absolute difference between the search threshold value and the first absolute speed value is greater than an absolute difference between the search threshold value and the second absolute speed value to determine which of the first position sensor and the second position sensor is abnormal accordingly. 
     
     
       13. The method of  claim 10 , further comprising when the absolute difference between the third absolute speed value and the fourth absolute speed value is greater than the threshold value, setting the first absolute speed value or the second absolute speed value as a search threshold value to determine which of the third position sensor and the fourth position sensor is abnormal accordingly. 
     
     
       14. The method of  claim 13  further comprising when the search threshold value is between the third absolute speed value and the fourth absolute speed value, determining whether an absolute difference between the search threshold value and the third absolute speed value is greater than an absolute difference between the search threshold value and the fourth absolute speed value to determine which of the third position sensor and the fourth position sensor is abnormal accordingly. 
     
     
       15. The method of  claim 8 , wherein when the comparison circuit receives a normal signal indicating all position sensors are normal, the calculation circuit calculates the first torque value of the first sensing loop and the second torque value of the second sensing loop according to the detection values of the first, second, third and fourth position sensors at the beginning of the preset time period, a parameter of the reduction drive, and a reduction ratio. 
     
     
       16. The method of  claim 8 , wherein when the comparison circuit receives an abnormal signal indicating that at least one of the position sensors is abnormal, the first torque value and the second torque value are not calculated. 
     
     
       17. The method of  claim 10 , further comprising:
 when a search signal indicates that the first position sensor or the third position sensor is abnormal, the torque output circuit outputting the second torque value; and 
 when the search signal indicates that the second position sensor or the fourth position sensor is abnormal, the torque output circuit outputting the first torque value.